Project Round Trooper Locks Up	Short Cuts
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By: Steve Kramer, Randy Burleson - 02/2001

ARB Air Locker Step by Step Install
in an Isuzu Trooper

The ARB kit comes fully equipped with everything required for the install.

The ARB locker is a user-selectable locker; it can either behave like an open differential, with no direct connection between the axles, or a spool, with both axles locked to the ring gear. This degree of control allows flexibility that limited slips and auto-lockers just can't match...

User control allows drivers to 'baby' front drivetrain parts like U-joints, Birfield joints, and CV-joints, locking these up only when necessary to surmount an obstacle. Spools and auto-lockers stress these expensive parts continually -- even between obstacles. This particular installation is on a rear drive axle, but rear axles do occasionally fail, so stress reductions out back are also of value.

Need to navigate a steep icy sidehill? Turn off that locker and drive straight across. With an auto-locker, the locked end will crab downhill... and that can be hard to control. Need to make a tight U-turn on sticky slickrock? Flip off the air locker, make that U-ey, then lock it back in for full traction. With an auto-locker, tight U-turns are cause for an upper-body workout, backing and filling while rowing the wheel from lock to lock. These are just a few advantages of the ARB air locker... the only real disadvantage may be one oft-argued by auto-locker owners: the ARB has more moving parts. True, there are more moving parts, but well-installed ARB lockers rarely fail. The big strikes against ARB is the complexity of install and its price; this article overviews the installation, but the entry price is definitely more expensive than an auto-locker. Users will have to determine whether the user-selectable flexibility benefits outweight the added costs.

CALMINI chose the ARB air locker for their Project Round Trooper because of its flexibility. They drove it from Bakersfield, CA to Moab, UT for the third annual Moab 'Zu Zoo event. When this Trooper arrived, Eddie toggled that air locker on and off as required for completion of several rugged trails. At the end of the trip, he turned it off for the long ride home.... talk about flexibility!

Installation

Installing an ARB locker requires care, but can be done by any shop with the correct tools and experience setting up a ring and pinion. Installers don't have to do a full gear setup, since the pinion gear depth doesn't have to be reset. Installing a new differential carrier does require that the backlash be reset, though, and it is a good practice to run a gear mesh pattern, as well, for insurance.

1. Remove rear wheels.	2. Remove rear brake calipers.	3. Remove rear drive line.
4. Remove rear axle bearing retainers, and prepare to remove axles.	5. Remove rear axles.	6. After draining rear differential fluid, remove bolts from rear third member housing.
7. Remove Third Member assembly from axle housing.	8. After removal from axle housing, clamp Third Member into a bench vise for disassembly. Remove carrier bearing caps and remove stock diff unit from Third Member.	9. Remove ring gear from stock diff unit. Remove carrier bearings or replace them with new bearings as needed.
10. Install carrier bearing on new Air Locker diff unit. Here we are using a small H-frame press.	11. Mark the Third Member housing for the location of the incoming air line brass bulkhead fitting. Drill hole for fitting.	12. Tap same hole for fitting.
13. Fit checking the Air Locker unit with the seal housing in place.	14. The seal housing tube must pass through the bearing cap. Mark and drill.	15. Install bearing caps with seal housing tube passing through bearing cap.
16. Bend seal housing tube to protrude through the tapped hole for bulkhead fitting in Third Member housing.	17. Remove Air locker housing from Third Member. Cut seal housing brass line to proper length. Install bulkhead fitting hardware to complete install of air seal. Assemble Air Locker unit into Third Member and complete process of setting ring gear backlash and carrier bearing pre-load.	18. Install complete assembly into axle housing. Re-fill axle housing with oil. Re-install axles, bearing retainers, and brake calipers.
19. Locate an open spot on the inner fender well to mount the air compressor unit. On our project trooper, the use of the CALMINI Hi-Flow Filter gave us plenty of room at the front of the driver's side inner fender well for the compressor and all related wiring and plumbing.		20. Routing of the air line to passenger side of engine bay for routing down the passenger side of the chassis to rear axle.
21. After routing the supplied wiring loom through the firewall, we chose to use two of the three available "knockout" panels on the left side of the Trooper's dash panel to install the Air Locker Differential and Compressor control switches. Follow the clearly labeled wiring loom tags for proper order of connection of Compressor and control solenoids.		22. Install Air Locker Control switches into dash panel. Apply AIR LOCKER warning decal to dash panel in area visible to driver.